Refining of fatty oils



June 17, 1941.

Fat ty oil Fatty oil.

A. U. AYRES REFINING OF FATTY OILS Filed Feb. 28, 1939 Mixer Oil Ce ncr 11+ u e M ixer Cenf rifug e Oil.

Hggldmzmior Emulsor Heater i8 Water MLS co Separcuor Soap Stock 5 Qlkcxli 1 I (5. 2 Cen'krtfuge Colloids Mixer FIG?) Cenfrifuge (Soap Siock Mixer INVENTOR- \Qrthur U Hyres ATTORNEY Patented June 17, 1941 UNITED STATES PATENT OFFICE REFINING F FATTY OILS Arthur U. Ayres, Chestnut Hill, Pa., assignor to l The Sharples Corporation, Philadelphia, Pa., 9. corporation of Delaware Application February 28, 1939, Serial No. 258,874

13 Claims.

The present invention pertains to the refining of fatty oils. It is particularly useful in the refining of vegetable oils. Among oils which can be profitably refined in accordance with the invention are the various fatty oils derived from vegetable sources, such as cottonseed oil, soya bean oil, palm oil, peanut oil, corn oil, cocoanut oil, etc.

The present invention was conceived as an improvement over the vegetable oil refining process described and claimed in the co-pending application of Edward M. James, Serial No. 567,220 (corresponding to British Patent 407,995). That process has been almost universally adopted in the vegetable oil industry of the United States and has resulted in very considerable loss-saving as compared with the kettle refining process which it replaced.

The object of the present invention has been to provide a process which would have all of the advantages of the aforementioned James process with respect to quality of oil produced, economy of space and simplicity and umformity of operation, and would have the additional advantage of affording a still further saving over that obtained in the practice of the James process.

An additional object of the present invention has beento provide a process by which a more fiuid'soap stook is obtained than in the practice of the James process, and in which the soap stock may therefore be discharged with more facility from the centrifugal apparatus employed to efie'ct separation of soap stock from refined oil. This feature is particularly advantageous in the treatment of oils which produce, upon refinifig, a relatively hard and non-fluid soap stock, such as cocoanut oil. By the practice of the features of' the present invention, oils having these characteristics may be refined with facility, without difficulty in connection with discharge of the soap stock from the'centrifugal rotor or from the covers to which the soap stock isp'assed from that rotor, although unusual difiiculty is encountered in connection with such discharge by continuousrefining processes heretofore employed.

'A' still further object has been to provide a process which, while possessing the advantages discussed in the two preceding paragraphs, would produce refined oil of superior quality to that produced by the James process, particularly in connection with the treatment of certain oils which present unusual difiiculties in refining, such as oils obtained by pressing in presses of the so-called Expeller type; i. e., presses in which the oil is expelled from the seed by a screw (e. g. the Anderson Expeller) as distinguished from the hydraulic bag presses. V

In the process of refining described in James patent application 567,220, the oil is first continuously mixed with alkali by violent agitation in a mechanical mixer. The mixture so produced is then maintained under relatively quiescent conditions for a short period of time during continuous flow to eifect agglomeration of dispersed soap stock particles, and this mixture is thereafter subjected to centrifugal separation at a temperature within the "break" point of the oil under treatment, e. g., at a temperature between 115 F. and 160 F. The James application is believed to represent the first introduction to the refining industry of a continuous centrifugal refining process embodying the principle of quickly agglomerating soap stock before passing it into a centrifugal separator, and the application of this principle to the problem of continuous refining is believed to represent the principal reason for the success of the James process as contrasted to prior attempts at continuous centrifugal refining.

The process of the present invention may include the features of the James continuous refining process involving agglomeration of soap stock between the steps of mixing and centrifugal separation, or it may involve an alternative method of performing the alkali treating and refining steps as described in my co-pending application, Serial No. 235,945, entitled Refining of fatty oils, filed on October 20, 1938, as will be more fully'pointed out hereinafter.

The present application is a continuation in part of my prior applications, Serial Nos. 235,945 and 235,946, respectively, both filed on October 20, 1938, and both entitled "Refining of fatty oils."

Further objects and advantages of the invention and the manner in which the above and such further objects have been attained in the practice of the invention will be obvious from a reading of the following specification in the light of the attached flow sheet, in which,

Fig. 1 illustrates the practice of one form of the invention.

Fig. 2 illustrates the practice of an alternative form of the invention, and

Fig. 3 illustrates the practice of a third form of the invention.

The inventionmay be practiced successfully by a number of different alternative sequences of steps, and features of the invention also include details as to particular concentrations and proportions of reagents and water employed in the refining operation. For the sake of simplicity of description, the invention will first be described with reference to the three figures of the attached flow sheet by way of a broad description of the sequences of operation illustrated in the fiow sheet, and the features of the invention pertaining to particular proportions and concentrations of refining agents will be described thereafter.

Referring to Fig. 1 of the flow sheet, fatty oil from container l may first be mixed with a small proportion of water from container II. This is preferably accomplished by metering a small proportion of water (e. g. A to 5%, based on the weight of the oil under treatment) into a flowing stream of oil. This metering operation is preferably performed by apparatus capable of effecting a very accurate proportioning of water to oil and capable of being adjusted to vary that ratio by adjustment of the metering apparatus either before commencing the continuous flow of the oil and water, or after that flow has been commenced, and during the continuous functioning of the process. An example of metering apparatus found to be particularly useful in this connection is the metering apparatus illustrated in Jones Patents Nos. 2,058,889 and 2,009,890.

The mixture of oil and water produced by introduc'ing a proportioned quantity of water continuously into the flowing stream of oil as described above is next passed through continuous mixing apparatus to effect fine dispersion of the added water throughout the body of oil under treatment. Thus, the mixture of oil and water is passed through a mixer l2, which may be a mechanical agitator through which the oil and water flow, a mixing nozzle adapted to effect fine dispersion of the water in the oil by sudden release of pressure, or any other well known form of mixing apparatus designed to fulfill this function.

Alkali from container I3 is thereafter added to the mixture of oil and water while the water is still in finely dispersed form throughout the body of the oil. This mixing of alkali with the mixture of oil and water is preferably accomplished by proportioning apparatus such as that illustrated in the two Jones patents discussed above in connection with the metering of water into the flowing stream of oil. The mixture of alkali with the oil and water is thereafter subjected to a further violent mixing action by passing this mixture through a mixer M which may be a mixer similar to the mixer l2 discussed above. The alkali is thus finely dispersed throughout the body of the oil and reacts with the fatty acid content of the oil to produce soap stock in well known manner.

The steps of mixing the water and alkali with the oil may be accomplished in accordance with this embodiment of the invention while the oil is relatively cold (e. g., between 70 and 100 F.), or the oil may be preheated before its contact with water and alkali. Thus, the oil may be heated to a temperature of between 100 and 180 F. in the container it, or it may be continuously heated to a temperature within this range (e. g. 140 F.) during its flow from the container l0 to the zone of confluence of the flowing stream of oil with water from the container ll. As a still further alternative, the oil may be heated to a temperature within the range of 100-180 F. after its confluence with water and before its confluence with alkali, by applying heat to the mixture in a zone between the zone of confluence with water and the mixer l2, or applying heat to the mixer l2 itself.

As a still further alternative, the oil may be passed through the mixer i2 and heated to an elevated temperature such as described above during its passage from the mixer l2 into confluence with the alkali from the container [3, or

it may be heated to such temperature between the zone of confluence with alkali from the container l3 and the mixer ll, or while it is in the mixer I 4. Best results in the practice of the invention have been obtained in cases in which the mixture of fatty oil and water was heated to a temperature of approximately F. (in case the oil is fluid at 140 F.) after confluence of the water with the oiland before mixing the alkali with the oil. In the treatment of certain oils, such as cocoanut oil and tallow, it will be desirable to heat the oil to a temperature between and 200 F. prior to treatment with alkali.

Regardless of the particular points of application of heat, it is desirable in the practice of the form of the invention illustrated in Fig. 1 that the oil or the mixture of oil and soap stock be heated to a temperature sufllciently high to cause the soap stock to break before the mixture is ultimately subjected to centrifugal separation to separate soap stock from oil as described hereinafter. As a further step in the practice of the invention in accordance with the embodiment of Fig. 1, the mixture .ofpil and soap stock is subjected to a step of agglomeration to cause coalescence of finely divided soap stock particles into larger particles before passing the mixture to the centrifugal separator. This is accomplished by passing that mixture through an agglomerator II, where it is subjected to quiescent conditions for a period which may vary between one-half minute and ten minutes. This agglomerator may consist of any type of apparatus through which the mixture passes under non-turbulent conditions, and the function of this agglomerating step is to facilitate subsequent centrifugation, in accordance with the well known law of physics that subsidence separation may be accomplished more efficiently on an impurity of larger size than an impurity of smaller size (Stokes law). In case the mixture of oil and soap stock is at a temperature less than the desired temperature for centrifugal separation (e. g., 115-160 F.) at the time it reaches the agglomerator IS, the agglomerator may comprise a heater of any conventional form (e. g., a pipe, coil or electric immersion heater) designed to heat the mixture to the desired separating temperature at the same time that the mixture flows quiescently through the heater to effect agglomeration of soap stock.

The mixture of oil and soap stock formed by the steps hereinabove described is passed from the agglomerator ii to a centrifugal separator it, which is preferably a centrifuge of the separator" type; i. e., a centrifugal separator designed to cause subsidence of soap stock to the circumferential wall of the rotor and formation of an oil stratum within the soap stock stratum so formed, and separate discharge of the oil and soap stock as separate efliuents from the rotor and covers of the centrifugal separator continuously.

It will be obvious that the process as described above incorporates the fundamental feature of James application 567,220, in that an agglomeration of dispersed soap stock particles is accomplished between the stage of the process at which the alkaline refining reagent is finely dispersed in the oil to form soap stock, and the stage at which centrifugal separation of soap stock from the refined oil takes place. It will be further evident that the process as so described presents the fundamental distinguishing feature over the process of the James application that the oil is mixed with a small quantity of water, and that the alkaline refining reagent is introduced into and mixed with the oil while this separately added water is still finely dispersed throughout the oil.

This distinguishing feature results in the attainment of important technical advantages in the process of continuous refining. The reasons for these advantages are not fully understood, but the advantages themselves have been established by an elaborate program of research on a commercial scale, and may be summarized as follows: As pointed out above, the problem of refining certain vegetable oils by a continuous process including centrifugation presents a diflicult problem because of the formation of a relatively hard and non-fluid soap stock when such oils are treated with alkali. Cocoanut, babassu, palm kernel and tallow oils present particular difiiculties because of this factor, since these hard, semicrystalline soap stocks tend to stick to the wall of the centrifugal rotor and to the covers into which they are discharged from the centrifugal rotor and through which they leave the centrifugal machine. It has been found that, by the practice of the step of separate water addition described above, the soap stocks later produced in continuously refining these oils are of much softer consistency and are much more fluid than soap stocks more conventionally produced in continuous refining. As a result 6f this fact, soap stock produced by the present invention may be readily discharged from the centrifugal machines employed in separation. While this feature has a particular advantage in the refiing of the particular oils discussed above in the present paragraph, it is also advantageous in the refining of any fatty oil, since increased fluidity of the soap stock represents an improvement in any refining process in that it increases the feasible period of continuous operation between periods of necessity for discontinuing that operation to clean the centrifugal machines.

The process described above also has important advantages in connection with the refining of expeller oil. The refining of this type of oil presents unusual problems, whether the oil is refined by the older kettle process, or by the James continuous process. If expeller oil is refined by a process identical with a process of refining hydraulic oil from a similar source, it will be found that the refined oil color of the expeller oil is darker than that of the corresponding hydrau- 1 ho oil. It has been discovered heretofore than this dark refined oil color can be improved by conducting the refining operation of expeller oil at somewhat lower temperatures than the temperatures employed in refining hydraulic oil from the same source. This lower refining temperature does not, however, solve the real problem involved, for the bleach color of expeller oil refined to a relatively light color by the use of lower temperatures is found to be higher than the bleach color of the corresponding hydraulic oil, even in cases in which the expeller oil at the conclusion of the alkali refining operation has the same color as the alkali-refined corresponding hydraulic oil. The apparent advantage in the use of low temperatures in refining expeller oil is thus found to be largely illusory, in that an advantage in ultimate bleach color corresponding to the advantage which would appear to be present upon examination of thealkali-refined expeller oil before bleaching is not attained. In the practice of the present invention, for some reason, a bleached oil of very greatly improved color is obtained by the ultimate bleaching step which follows alkali refining. The sequence of refining and bleaching thus results in the production of a bleached oil having a color comparable to bleached oil produced by refining and bleaching hydraulically pressed crude oil.

In addition to the advantages obtained by the practice of the invention in the treatment of cocoanut oil, palm kernel oil, babassu oil, tallow and expeller oil, as discussed above, a very considerable increase in yield is obtained in the refining of any fatty oil by the practice of the invention as compared to the yield obtained when the oil is refined by the conventional James refining process.

While advantagesas to fluidity of soap stock and yield are obtained in the treatment of fatty oils in general by the practice of the invention, and particular advantages are obtained in the treatment of expeller oils, palm kernel oil, cocoanut oil, etc., an attendant disadvantage is encountered in the practice of the invention in the refining operation as described above. For some reason, it is more diflicult to obtain adequate removal of soap stock from oil when employing the step of separate water addition which characterizes the invention than when this step is omitted. As the result of this increased difliculty of separation of soap stock from the refined oil, it is necessary to employ some special precaution, such as reduction of the rate of feed of oil to the centrifugal separator or increased centrifugal force, if oil is to be discharged from the centrifugal separator which has a soap stock content as low as that which can be obtained by the James continuous refining processas heretofore commercially used.

In the preferred form of the invention, this difiiculty is overcome by employing a prompt centrifugal water washing process on the oil discharged from the centrifugal separator. By employing this additional step, it is found that the soap stock content of the oil discharged from the refining centrifuge may be considerably higher than that of the prior James process without reducing the efficiency of the process as a whole.

In the practice of the present invention, the oil discharged from the centrifuge l6, which may contain a considerably higher proportion of soap stock than oil discharged by the refining centrifuges heretofore used in the practice of the James process, is treated promtply for the removal of soap stock. This treatment may involve promptly heating the oil to a temperature between 140 and 180 F. (e. g. 160 F.) by passing it through a continuous heater H. The heated oil is thereafter mixed with warm water from container I 8, and the mixture may be passed through a mixer I9 of the same character as the mixers l2 and I4 discussed above. The soap content of the oil is associated with the wash water in the mixer l9 and the mixture is there after passed to a centrifugal separator 20 of the same type as the centrifugal separator l6 discussed above. Oil and wash water containing soap are continuously discharged from the centrifugal separator 20 as separate efiluents under liquid balance against each other,

In the form of the invention illustrated in Fig. 2 of the fiowsheet, the initial step of addition of a small quantity of water is practiced in the same way as in the embodiment of Fig. 1, but this embodiment of the invention involves a process of the general character of the process of my prior application Serial No. 235,945, filed October 20, 1938, and omits the step of agglomerating the soap stock prior to passage to the centrifugal separator.

As illustrated in Fig. 2 of the flow sheet, oil is passed from container ll into confluence with water from container 3i and the oil and water are mixed together in a mixer 32. These three initial steps of the process may be identical with the initial steps of the process described above in connection with Fig. 1 of the fiow sheet. The oil may be heated in the container 30, or it may be heated in transit from the container 30 to the zone of confluence with water from container Si, or it may be heated after being mixed with water from container ll, as described above in connection with Fig. 1 of the fiow sheet. The oil is preferably heated after water is finely dispersed therein by'the action of mixer 32, as, for example, by passing it through a continuous heater II, which may be any one of the types of heater discussed above in connection with agglomerator I! of Fig. 1 of the fiow sheet. Alternatively. the process of Fig. 2 of the fiow sheet may be performed at low temperatures (e. g., below 115 F. if the oil is fluid at such temperatures), but the ei'ilciency of the process in separating soap from oil is usually materially reduced if such low temperatures are employed.

The oil containing the added water still finely dispersed therein, and preferably heated to a temperature between 115 F. and 160 F. or even higher by passage through the heater 33. is next mixed with caustic soda or other refining alkali from the container 34. The mixture so formed is then passed directly to a centrifugal machine 35 of the general type illustrated in the French patent to P. T. Sharples, No. 522,744, or the patents to Jones, Reissue No. 17,719 and No. 1,649,118. Such machines are designed to effect intimate mixing between the alkali and oilin one end of the centrifugal rotor and to effect subsidence separation and continuous discharge of separated ingredients from each other from another part of the same centrifugal rotor. In the embodiment illustrated in Fig. 2 of the flow sheet, alkali is intimately mixed with the oil in the lower end of the misco-separator centrifugal machine 35 and is thus finely dispersed throughout the oil to effect reaction of the alkali upon the fatty acids and other impurities of the oil and formation of soap stock in well-known manner. The mixture of oil and soap stock is thereafter subjected to subsidence separation in the same centrifugal rotor, and the soap stock is thus separated from the oil.

The method of operation discussed above, consisting in efl'ecting mixing of the oil with the refining alkali in a centrifugal rotor and separation of soap stock from oil in that same centrifugal rotor, is even superior to that described in connection with Fig. 1 of the fiow sheet. While agglomeration of soap stock is desirable from the standpoint of promoting eificiency of separation of soap stock from oil, a part of the function of the centrifugal separator in any continuous centrifugal refining process consists in the action of squeezing out entrained oil from soap stock particles. In the practice of the form of the invention illustrated in Fig. 2 of the flow sheet, the soap stock particles are not given an opportunity to agglomerate prior to centrifugal separation, and they do not therefore have the same tendency to entrain neutral oil as in the James continuous process or in the process illustrated in Fig. l of the fiow sheet.

While the step of agglomeration as taught in James application Serial No. 567,220 is eliminated with an attendant advantage in the process of Fig. 2 of the fiow sheet, as described above, the elimination of the agglomerating step necessarily renders the step of centrifugal separation more dimcult to perform. Thus, the oil discharged from the centrifugal machine II of Fig. 2 of the flow sheet has an even higher content of soap stock than the oil discharged from the centrifugal separator ll of Fig. 1 of the flow sheet. In order to offset this disadvantage, the oil is very promptly washed with water after discharge from the centrifugal machine 35, in the same manner as illustrated in connection with reference numerals II to 20 of Fig. 1 of the fiow sheet. or in accordance with the teaching of James Patent No. 2,050,844, patented August 11, 1936, for Method of refining vegetable oils."

When the invention is practiced in accordance with the procedure illustrated in Fig. 2 of the flow sheet, all of the advantages discussed above in connection with Fig. 1 of the fiow sheet are obtained in the treatment of cocoanut oil, babassu oil, palm kernel oil, tallow and expeller oil. Furthermore, the practice of the invention as illustrated in Fig. 2 results in aneven better yield of refined oil regardless of the source of the crude oil, than does the invention as illustrated in Fig. 1.

Fig. 3 of the fiow sheet illustrates a still further form of the invention, which may be used in the refining of any fatty oil, but which is particularly useful in the refining of expeller oils.

As pointed out above, oils obtained from expeller presses cannot ordinarily be bleached after a1- kali refining to produce bleached oil of color comparable in oils obtained by hydraulic pressing. In the embodiment of Figs. 1 and 2 of the flow sheet, expeller oils are refined by dispersing water finely throughout the body of the oil and continuously refining with alkali while the water is still finely dispersed. This step of dispersing water through the expeller oil prior to alkali refining, for some reason renders the subsequent alkali refining process effective to remove from the oil impurities which would otherwise impair the ultimate bleach color.

In the embodiment of Fig. 3 of the drawing. the water finely dispersed in the oil is removed from the oil together with impurities precipitated by the water treatment, and this step of removing the water together with associated colloids prior to alkali refining results in production of an alkali refined oil which may be bleached to produce a bleached oil of a color comparable to that produced in the practice oi the invention as illustrated in Figs. 1 and 2 of the flow sheet. In the practice of the invention in this embodiment, fatty oil from container 40 is first mixed with water from container ll by passing the oil and water (which may comprise between one-half and five percent of the mixture) through a mixer 42 which may be similar to the mixer i 2 of Fig. 1.

The exact function of the water in improving the character of expeller oil by this treatment is not fully understood. Apparently, oil obtained from an expeller press contains some vegetable impurity or carbon not present in oil obtained by hydraulic pressing. -In any case, the addition of water in a small proportion, and the thorough mixing of the water with the oil as discussed above. appears to cause precipitation of certain finely dispersed colloidal material which is successfully removed from the oil by the centrifuge 43, but which would otherwise prevent the ultimate successful bleaching of the oil. The oil, or the mixture of oil and water, may be heated, continuously or in batch, to a temperature between 100 and 200 F. at any time before or after the mixture is formed, and before it is passed to the centrifugal separator 43.

The oil, which has been freed of colloidal impurities by the action of the centrifuge 43 as discussed above, is next mixed with alkali from container 44. This mixture is then passed through a mixer 45 to effect fine dispersion of alkali throughout the oil with attendant formation of soap stock, and the mixture of oil and soap stock so formed may then be passed to a centrifugal separator 46 which effects removal of soap stock from oil. Oil discharged from the centrifugal separator 46 is preferably washed with water promptly Just as in the cases of the oil discharged from the centrifugal machines 16 and 35 discussed in connection with the embodiments of Figs. 1 and 2 of the flow sheet.

While a sequence of alkali refining operations involving passing the oil and alkali together through a mechanical mixer and from that mixer to a centrifugal separator 46 has been described above in connection with the embodiment of Fig. 3 of the drawing, it will be evident that any of the sequences of alkali refining employing or omitting an agglomerating step or employing or omitting the use of a centrifugal machine of the misco-separator type, may be used in the practice of the steps indicated by the reference characters 44 to 46 in Fig. 3 of the flow sheet.

As pointed out above, some difiiculty is encountered in effecting efiicient removal of soap stock from oil in the treatment of most fatty oils in accordance with any one of the three embodiments of the invention as described above. An important feature of the invention consists in the discovery that this difficulty may be minimized by employing unusually strong alkaline solutions in the refining operations. Thus, in the treatment of most oils in the practice of all three of. the embodiments of the invention, it is desirable that an alkaline reagent be employed which is of substantially stronger concentration than that ordinarily used in kettle and continuous refining of the particular oil under treatment. By the use of caustic soda of unusually high concentration, for example, the soap stock may be efficiently separated from the refined oil. By using a reagent of higher strength than conventional, the overall loss of oil in the practice of the refining operation is substantially less than would be entailed in continuous refining of oil by the James continuous process or the prior art kettle process. Thus, while the efficiency of the primary separaation is reduced in the practice of any one of the three embodiments of the invention discussed above, the difficulty in separation may be minimized by the use of concentrated refining reagents.

As an example of the difference in alkali concentration employed in the practice of the present invention as contrasted to prior kettle and continuous refining, it may be pointed out that, in cases in which a 16 Baum solution has been used in prior refining practice, a 22 Baum solution affords best results in the treatment of the same oil in the practice of. the present invention. In any case, it is desirable to use a concentration of caustic soda (in case that reagent is used) in the practice of the present invention which is at least at'strong as 20 Baum, even though the oil be of such low free fatty acid content that it is ordinarily refined by caustic soda solution as low as 12 or 14 Baum in accordance with the 1937 rules of the National Cottonseed Crushers Association.

In the practice of the invention in accordance with the form illustrated in Fig. 1 of the fiow sheet, the amount of alkaline reagent used (on a dry basis) is also reduced substantially below the amount which would be necessary to eifect kettle or continuous refining of the crude oil in accordance with the kettle process or the James continuous process. Thus, in cases in which the 1937 rules of the National Cottonseed Crushers Association prescribe a refining treatment with 8% of 16 Baum caustic soda solution, best results are usually obtained in refining in accordance with Fig. 1 of the flow sheet by the use of approximately 3.5% of 22 Baum caustic soda solution.

In the practice of the invention as illustrated in Fig. 2 of the fiow sheet on most oils, the concentration of the alkaline solution is preferably substantially the same as that discussed above in connection with the embodiment of Fig. 1, but the total quantity of alkaline solution employed in treatment in accordance with Fig. 2 of the flow sheet should be somewhat greater than the total quantity used in the embodiment of Fig. l. The fact that the oil passes directly from the step of intimate mixing in the base of the centrifugal machine 35 to the stepof centrifugal separation in the upper part of that machine causes a reduction in the total time of contact between oil and alkali, and it is therefore necessary to employ a larger proportion of alkali (on a dry basis) in the practice of the form of the invention illustrated in Fig. 2.

In the embodiment of Fig. 2 of the invention. the use of a large excess of alkaline reagent enables the operator to effect the desired removal of fatty acids and coloring matter from the oil, in spite of the fact that the total time of contact between oil and alkali is less than one minute, being usually only about one-half minute.

For example, in the treatment of a typical cotton seed oil in which 8% of 16 Baum lye is prescribed by the 1937 rules of the National Cottonseed Crushers Association, it has been found that 3.5% of 22 Baum lye gives best results in the practice of the invention in accordance with Fig. 1 of the flow sheet, and that 8% of 22 Baum lye gives best results when the embodiment of Fig. 2 is practiced.

The concentration of alkali employed in the practice of the invention as illustrated in Fig. 3 should be similar to that discussed above in connection with Figs. 1 and 2. In the practice of this form of the invention, the ratio of alkali to oil will be the same as that discussed above in connection with Fig. 1 of the flow sheet in case the soap stock is allowed to agglomerate before reaching the centrifugal separator 46, but it will be approximately the same as that discussed in connection with Fig. 2 of the flow sheet in case the step of agglomeration is omitted, as, for example, by omitting the mixer 45 and employing a centrifugal machine similar to the misco-separator 35 of Fig. 2 of the fiow sheet in place of the centrifugal separator 46.

An exception to the above discussion concerning the concentration of alkali to be used in the practice of the refining operation occurs in cases in which oils of the character of babassu, palm kernel, cocoanut or tallow are refined, since the hardness and lack of fiuidity of the soap stock produced when alkali of high concentration is used causes difficulty in discharge of soap stocks from these oils from a centrifugal. Thus, in the treatment of these particular oils, the best results are obtained in the practice of the invention by employing caustic soda of 16 Baum concentration in cases in which the 1937 rules of the National Cottonseed Crushers Association call for use of Baum caustic soda in the treatment of such oils. While the use of these lower concentrations of caustic soda in the treatment of particular oils reduces the yield of oil obtained by causing loss of some oil in the soap stock by emulsification, this loss is economically offset by the increased fluidity of the soap stock and the improved general efficiency of the process obtained by the fine dispersion of water in the oil prior to the alkali refining step.

In the treatment of a small proportion of crude oils in accordance with the process illustrated in Fig. 2 of the flow sheet, it will be found that the oil discharged from the centrifugal machine 35 is darker in color than oil refined by more conventional processes. This darkness of color, in connection with certain crude oils presenting unusual difiiculties in refining, is due to inadequate mixing or to inadequate time of contact between the oil and alkali. In the treatment of such oils, the oil and alkali may be passed through a centrifugal emulsor 35 before being passed to the centrifugal machine 35, as illustrated in the flow sheet. The use of the centrifugal emulsor affords a longer time of mixing and a more thorough mixing of oil and alkali than can be obtained in the centrifugal machine 35 alone, and thus obviates all of the dimculties encountered in the treatment of the small proportion of oils which cannot be adequately refined by the mixing action of the centrifugal machine 35 alone. In cases in which a separate centrifugal emulsor 35 is used, a smaller ratio of alkali to oil will be required than in cases in which the entire mixing and separating function is accomplished in a single centrifugal machine, such as the machine indicated by the numeral 35. The centrifugal emulsor 35 may be any suitable form of centrifugal mixing machine, such as the machine illustrated in Fig. 3 of the French patent to P. T. Sharples, No. 522,744.

In the practice of the invention in accordance be 15 minutes, or less, and the entire time consumed in the water washing operation after the completion of the alkali refining step will ordinarily be 30 minutes or less. In the practice of the invention as illustrated in Fig. 2 of the drawing, the total time of contact between oil and alkali will ordinarily be less than 5 minutes, and is preferably of the general order of 1 minute or less. The steps of mixing oil with water, mixing oil with alkali, ag'glomerating and centrifuging are thus rapidly and continuously performed, and it is also preferable that the step of heating be performed continuously, since best economy in heat transfer and space is accomplished by means of a continuous heater. As pointed out above, however, the oil may be heated in the crude oil container before being passed through the steps of the process, and the water may be added to the oil and dispersed throughout the body of the oil in this crude oil container before the continuous flow of the oil through the steps of the process starts, if desired. In case the water is dispersed through the oil before the flow of the oil through the steps of the process, it is preferable that the oil in the crude oil container be agitated after the addition of the water and during the fiow of the crude oil through the steps of the continuous refining process, since it is desirable that subsidence of colloidal material precipitated by the addition of the water be avoided until after the crude oil is mixed with alkali to form soap stock.

In the runs tabulated in the following specific examples, a sample of the vegetable oil to be refined was first treated by the best batch prior art procedure for refining. A second sample was thereafter treated by the James continuous process under the most favorable conditions, and a third sample was treated by the process of the present invention, as indicated in the tabulation. The data as to the quantity and strength of caustic soda used, the color of the refined oil, the color of the bleached oil, the refining loss, and the amount of water added, in cases in which water was added, are tabulated with respect to the dlfierent oils in the following specific examples:

Example 1 Hydraulic cottonseed oil having a free fatty acid content of 0.65% was treated in comparative with any one of the forms illustrated above, the tests with the following results:

223:, Alkali used Refined oil oolor Bleach color Percent Percent Batch process 5.5 of 14.... 5. 6 35 yellow, 5.5 red 14 yellow. 1.4 red James process 3. of 14.... 4. l 35 yellow, 5.2 15 yellow, 1.5 red Present process 2. 0 3. n of 22---. 3. 7 35 yellow, 5.5 red 10 yellow, 0.0 red fiorw of oil through the steps of the process will Example 2 preferably be rapid and continuous. Thus, the entire time consumed by a given particle of the oil in passing from the crude oil container through the refining centrifuge will ordinarily Expeller cottonseed oil having a free fatty content of 1.8% was treated in comparative tests with the following results:

f ag mm used gg Refined oil color Bleach cola- Btchprocess 8 120 108 yello 12 red 8 o. w, .2 35 ellow. 5.01mi. James process 5% of 25".-.. 7. 1 35 yellow, 10.9 red.-.-. 35 gcliow, 5.0 red. Present process 2. 0 10. a of 28.-. 7. 2 35 yellow, 12.2 red-.. 35 yellow, 3.8 rod.

Example 3 Hydraulic cottonseed oil having a free fatty acid content of 1.7% was treated in comparative those skilled in the art, and I do not therefore wish to be limited except by the scope of the subjoined claims.

I claim:

tests with the following results: 5 1. In the treating of fatty oils, a process com- 33 5;; Alkali used fi g Refined oil color Bleach color Percent 6.3% oi16 7. 5 35 yellow, 5.5 red 15 yellow, 1.3 red. 4.5% of 16.... 5. 7 35 yellow, 6.0 red 15 yellow, 1.4 red. 6.0% of 4. 8 35 yellow, 7.0 red 10 yellow, 1.1 red.

Example 4 prising, mixing between and 5% of water with the oil to be refined and finely dispersing the added water throughout the body of the oil, thereafter continuously refining the oil containing the added finely dispersed water by'mixing it Z2325; Alkali used 3%;? Refined oil color 353 Percent Percent Batch process 5.67 of 16. 11. 9 50 yellow, 3.7 red.

James process 5.6% M16". 8.2 50 yellow, 2.8 red.

Present process 2.0 3.6% of 22.. 7. 3 50 yellow, 2.8 red.

Example 5 Cocoanut oil having a free fatty acid content of 5.7% was treated in comparative tests with the following results:

with alkali to effect reaction of the alkali upon the free fatty acid of the oil to form soap stock, and promptly subjecting the mixture of oil and soap stock so produced to centrifugation to separate the soap stock from the refined oil.

Z2322; Alkali used figg Refined oil color 1323 Percent Percent Batch process 0.2% of 20-. 8. 1 6 yellow, 1.0 red. James process The centrifugal rotor became clogged with hard soap in all attempts at centrifugal refining Present process 3.0 l 7.6% of 16-.l l3. 7 8 yellow, 1.4 red. I

(In this est run, the soap stock was discharged from the centrifugal separator without difficulty) In the following claims, when reference is made to addition of alkaline reagent of higher reagent concentration than that employed in standard alkali refining of the crude oil, this expression is intended to define the use of an alkaline reagent of substantially higher concentration than that prescribed by the 1937 rules of the National Cottonseed Crushers Association for treatment of oil of the fatty acid content under treatment. In cases in which oils are treated which are not referred to in the 1937 rules of the National Cottonseed Crushers Association, the expressionis intended to define a treatment with alkali of substantially stronger concentration than that which would ordinarily be used in kettle refining of oil of the free fattyacid content of the oil under treatment.

When reference is made in the following claims to the addition of water to the oil, it is to be understood that this form of definition includes the addition of water either in a relatively pure state, or of water containing dissolved therein small quantities of electrolytes such as alkalies, acids or salts, or of starch. In case of the use of water containing these substances in solution, the solution should be very dilute. In cases in which an alkaline solution is added in place of the water in the practice of the invention, the amount of alkali contained in the Water preliminarily added will be substantially less than the amount of alkali which would be necessary to neutralize the fatty acid contained in the oil under treatment.

Still further modifications will be obvious to 2. In the treating of fatty oils, a process comprising, mixing between and 5% of water with the oilto be refined and finely dispersing the added water throughout the body of the oil, thereafter continuously refining the oil containing the added finely dispersed water by mixing it with alkali to effect reaction of the alkali upon the fre fatty acid of the oil to form soap stock, permitting the mixture of oil and soap stock so produced to remain quiescent for a brief period of time to effect agglomeration of the soap stock, and promptly thereafter subjecting the mixture of oil and soap stock so produced to centrifugation to separate the soap stock from the refined oil.

3. In the treating of fatty oils, 2. process comprising, mixing between /2% and 5% of water with the oil to be refined and finely dispersing the added water throughout the body of the oil, thereafter continuously refining the oil containing the added finely dispersed water by mixing it with alkali to effect reaction of thealkali upon the free fatty acid of the oil to form soap stock, and promptly subjecting the mixture of oil and soap stock so produced to centrifugation to separate the soap stock from the refined oil without permitting the soap stock in the oil to agglomerate between the steps of continuously mixing the alkali with the oil and the step of centrifugation.

4. In the treating of fatty oils, 2. process comprising, mixing between and 5% of water with the oil to be refined and dispersing the added water throughout the body of the oil,

thereafter continuously refining the oil containing the added finely dispersed water by mixing it with an aqueous alkaline reagent of higher reagent concentration than that employed in standard alkali refining of the crude oil to effect reaction of the alkaline reagent upon the free fatty acid of the oil to form soap stock, and promptly subjecting the mixture of oil and soap stock so produced to centrifugation to separate the soap stock from the refined oil.

5. In the treating of fatty oils which, upon conventional refining with alkali, form a hard and relatively non-fluid soap stock, a process comprising, mixing between /1% and of water with the oil to be refined and finely dispersing the added water throughout the body of the oil, thereafter continuously refining the oil containing the added finely dispersed water by mixing it with alkali to effect reaction of the alkali upon the free fatty acid of the oil to form soap stock, and promptly subjecting the mixture of oil and soap stock 50 produced to centrifugation to separate the soap stock from the refined oil.

6. In the treating of expeller fatty oils, a process comprising, mixing between and 5% of water with the oil to be refined and finely dispersing the added water throughout the body of the oil, thereafter continuously refining the oil containing the added finely dispersed water by mixing it with alkali to efiect reaction of the alkali upon the free fatty acid of the oil to form soap stock, and promptly subjecting the mixture of oil and soap stock so produced to centrifugation to separate the soap stock from the refined oil.

'7. In the treating of fatty oils, a process comprising, continuously mixing between and 5% of water with the oil to be refined and finely dispersing the added water throughout the body of the oil, thereafter continuously heating the mixture of oil and water so formed to a temperature between 100 and 180 F., thereafter continuously mixing the oil containing the added finely dispersed water with alkali to effect reaction of the alkali upon the free fatty acid of the oil to form soap stock, and promptly subjecting the mixture of oil and soap stock so produced to centrifugation to separate the soap stock from the refined oil. a

8. In the treating of fatty oils, a process comprising, mixing between /2% and 5% of water with the oil to be refined and finely dispersing the added water throughout the body of the oil, thereafter continuously refining the oil containing the added finely dispersed water by mixing it with alkali to effect reaction of the alkali upon the free fatty acid of the oil to form soap stock, promptly subjecting the mixture of oil and soap stock so produced to centrifugation to separate the soap stock from the refinedoil and promptly thereafter mixing water with the oil from which soap stock has been separated by said step of centrifugation and centrifugally separating the water added in said last-mentioned step and residual soap stock from the oil by a further step of centrifugation.

9. In the refining of fatty oils, a continuous process comprising, mixing between and 5% of water with the 'oil to be refined and finely dispersing the added water throughout the body of the oil, thereafter continuously passing the 011 containing the added finely dispersed water to a centrifugal rotor, mixing aqueous alkaline so lution with the oil in said centrifugal rotor, and separating the soap stock formed by said mixing operation from refined oil by centrifugation in the same centrifugal rotor.

10. In the treating of fatty oils, a process comprising, mixing between /2% and 5% of water with the oil to be refined and finely dispersing the added water throughout the body of the oil, thereafter-continuously refining the oil containing the added finely dispersed water by mixing it with an aqueous alkaline reagent of higher reagent concentration than that employed in standard alkali refining of the crude oil by passing said oil and alkaline solution through a centrifugal rotor designed to mix the same and thus form soap stock by reaction of the alkaline solution upon the free fatty acid of the oil, and promptly subjecting the mixture of oil and soap stock so produced to centrifugation in a second centrifugal rotor to separate the 'soap stock from the refined oil.

11. In the treating of expeller fatty oils, a process comprising, mixing between and 5% of water with the oil to be refined and finely dispersing the added water throughout the body of the oil, thereafter continuously refining the oil containing the added finely dispersed water by mixing it with an aqueous alkaline reagent of higher reagent concentration than that employed in standard alkali refining of the crude oil by passing said oil and alkaline solution through a centrifugal rotor designed to mix the same and thus form soap stock by reaction of the alkaline solution upon the free fatty acid of the oil, and promptly subjecting the mixture of oil and soap stock so produced to centrifugation in a second centrifugal rotor to separate the soap stock from the refined oil.

12. In the treating of fatty oils chosen from the class consisting of cocoanut oil, babassu oil, palm kernel oil and tallow, 'a process comprising, mixing between and 5% of water with the oil to be refined and finely dispersing the added water throughout the body of the oil, thereafter continuously refining the oil containing the added finely dispersed water by mixing it with alkali to effect reaction of the alkali upon the free fatty acid of the oil to form soap stock, and promptly subjecting the mixture ofoil and soap stock so produced to centrifugation to separate the'soap stock from the refined oil.

13. In the treating of fatty oils, a process comprising, continuously mixing between and 5% of water with the oil to be refined and finely dispersing theadded water throughout the body of the oil, thereafter continuously mixing the oil containing the added finely dispersed water with alkali to effect reaction of the alkali upon the free fatty acid of the oil to form soap stock, and promptly subjecting the mixture of oil and soap stock so produced to centrifugation to separate the soap stock from the refined oil.

ARTHUR UT AYRES. 

